Understanding particle-mediated contaminant transport through real-time monitoring

Aquatic particles represent a significant sink for hydrophobic contaminants including Poly-Chlorinated Biphenyls (PCB). The riverbed of the Hudson River near Ft. Edward, New York is contaminated with PCBs due to the discharge of these chemicals from two General Electric Company (GE) capacitor manufacturing plants into the river from approximately 1947 to 1977. The contaminated sediments continue to be an active PCB source to the water column and biota. GE initiated remedial dredging operations in 2009 to remove the contaminated sediments and subsequently reduce PCB concentrations in fish, river water and sediment, and to minimize downstream transport. To meet these objectives, Environmental Protection Agency (EPA) required GE to follow three engineering performance standards (production, re-suspension and residual) during the dredging operation. Data collected from the River and Estuary Observation Network (REON) are presented in this paper to provide evidence of the capability of the observation network in characterizing particle dynamics which can guide in adaptive dredging operation to meet the objectives, and to track the improvements of water quality due to this remediation action. In this study, the particle dynamics at the Thompson Island Pool (TIP), where high PCB concentrations are found in the sediment and biota, were characterized with respect to stream velocity profiles, suspended sediment concentration and particle size distribution during a flood event. This characterization presented sediment resuspension and advection as potential mechanisms for sediment and sediment bound PCBs transport during a flood event. Moreover, integration of the monitoring datasets with the PCB fate and transport model can serve as a valuable diagnostic tool for investigating the impacts of PCB on the ecosystem of the Hudson River.